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		[page:Object3D] &rarr; [page:Line] &rarr;

		<h1>[name]</h1>

		<p class="desc">
			渲染箭头辅助对象 [page:ArrowHelper arrows] 来模拟顶点的法线.
			需要定义了法线缓存属性 [page:BufferAttribute custom attribute] 或
			使用了 [page:BufferGeometry.computeVertexNormals computeVertexNormals] 方法计算了顶点法线.<br /><br />
		</p>

		<h2>代码示例</h2>

		<code>
		const geometry = new THREE.BoxGeometry( 10, 10, 10, 2, 2, 2 );
		const material = new THREE.MeshBasicMaterial( { color: 0xff0000 } );
		const box = new THREE.Mesh( geometry, material );

		const helper = new VertexNormalsHelper( box, 2, 0x00ff00, 1 );

		scene.add( box );
		scene.add( helper );
		</code>

		<h2>例子</h2>
		<p>
			[example:webgl_helpers WebGL / helpers]
		</p>

		<h2>构造函数</h2>


		<h3>[name]( [param:Object3D object], [param:Number size], [param:Hex color], [param:Number linewidth] )</h3>
		<p>
			[page:Object3D object] -- 要渲染顶点法线辅助的对象.<br />
			[page:Number size] -- (可选的) 箭头的长度. 默认为 1.<br />
			[page:Hex color] -- 16进制颜色值. 默认为 0xff0000.<br />
			[page:Number linewidth] -- (可选的) 箭头线段的宽度. 默认为 1.
		</p>


		<h2>属性</h2>
		<p>请到基类 [page:LineSegments] 页面查看公共属性.</p>

		<h3>[property:Object matrixAutoUpdate]</h3>
		<p>
			请查看 [page:Object3D.matrixAutoUpdate]. 这里设置为 *false* 表示辅助对象
			使用对象的世界矩阵 [page:Object3D.matrixWorld matrixWorld].
		</p>

		<h3>[property:Object3D object]</h3>
		<p>被渲染顶点法线辅助的对象.</p>

		<h3>[property:Number size]</h3>
		<p>箭头的长度. 默认为 *1*.</p>


		<h2>方法</h2>
		<p>请到基类 [page:LineSegments] 页面查看公共方法.</p>


		<h3>[method:null update]()</h3>
		<p>基于对象的运动更新顶点法线辅助对象.</p>


		<h2>源码</h2>

		<p>
			[link:https://github.com/mrdoob/three.js/blob/master/examples/jsm/helpers/VertexNormalsHelper.js examples/jsm/helpers/VertexNormalsHelper.js]
		</p>
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